This study was conducted to examine the utilization of immunohistochemistry using the bovine anti-brucella immunoglobulin G (IgG) antibody in the diagnosis of brucellosis and to develop a functional biomarker relation for the progress of the disease. Anti-brucella IgG antibody was purified from the affected bovine serum using an affinity chromatography. We performed our investigation on 17 cases of brucellosis and 19 control cases with negative Rose-Bengal test results. Our purified anti-brucella IgG antibody showed a positive immunoreactivity in cytoplasmic hepatocytes of the centrilobular region, and glomeruli and tubular epithelium of the kidney. The protein pattern of the affected liver versus control was analyzed by two-dimensional electrophoresis, showing a different expression pattern of proteins between the two. Five protein spots were up-regulated and another were five down-regulated in the brucellosis liver. Significant upregulaton of catalase and 3-hydroxyacyl-CoA dehydrogenase might be due to a compensatory reaction in response to the endotoxic shock of brucella. In conclusion, the anti-brucella IgG antibody may be a good tool for discriminative diagnosis of the affected tissues and proteomics data suggest new target proteins underlying a possible pathogenic mechanism of brucellosis.